The disclosures of Japanese Applications No. 11-203581 and No. 11-230860 are hereby incorporated by reference.
1. Field of the Invention
This invention relates to a thermochromic acrylic synthetic fiber having a thermochromic pigment contained dispersedly in an acrylonitrile polymer, its processed article, and a process for producing the thermochromic acrylic synthetic fiber.
2. Related Background Art
As a means for providing fibers with a thermochromic function, conventionally available are a means of covering fiber surfaces with thermochromic layers having a thermochromic pigment fixed dispersedly in a binder resin (Japanese Patent Applications Laid-Open No. 61-179389, No. 62-156355, etc.) and a means of melt-blending a thermochromic pigment in a thermoplastic fiber-forming polymer such as polyester, polyamide or polyolefin, followed by melt-spinning to form fibers in an integral form.
Now, in the case of the acrylic synthetic fiber, fibers can not be formed by melt spinning, melt-blending the thermochromic pigment integrally, because of thermal properties of the acrylonitrile polymer. Accordingly, it has been indispensable to form on fiber surfaces the above thermochromic layers by post-processing to provide the thermochromic function.
Hence, it has been unavoidable that the feeling or hand of acrylic fibers themselves is damaged and besides, compared with those melt-spinned by melt blending, the products are inferior in respect of durability such as wash-fastness, rub strength and light fastness.
Meanwhile, in the case of those obtained by melt spinning, the thermochromic pigment undergoes high temperature and high pressure in the course of its melt-blending with the fiber-forming polymer and in the course of melt spinning. This causes thermal deterioration of the thermochromic pigment in some cases. Accordingly, there has been obstruction to the use of fiber-forming polymers having high molecular weight and high melting point which are commonly applicable to fibrous products, and it has been difficult to practically satisfy durability such as fiber strength.
The present inventors made extensive studies to eliminate the above difficulties. Accordingly, an object of the present invention is to provide a thermochromic acrylic synthetic fiber, and its processed article, which can effectively lastingly exhibit the thermochromic function without losing the hand inherent in acrylic fibers and other fibrous features, and to provide a process for producing such a thermochromic acrylic synthetic fiber.
To achieve the above object, the present invention provides a thermochromic acrylic synthetic fiber comprising an acrylonitrile polymer in which a thermochromic pigment composition with an average particle diameter of from 0.5 xcexcm to 30 xcexcm is dispersedly contained in an amount of from 0.5% by weight to 40% by weight based on the weight of the polymer, and being made into fibers; the pigment composition containing (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound and (c) a reaction medium that determines the temperature at which the color-developing reaction of the both compounds takes place.
As a preferred embodiment of the above thermochromic acrylic synthetic fiber, the thermochromic pigment composition may have an average particle diameter [(length+breadth)/2] in the range of from 0.5 xcexcm to 15.0 xcexcm;
the thermochromic pigment composition may be a pigment composition having a microcapsular form in which a reversible thermochromic composition containing (a) the electron-donating color-developing organic compound, (b) the electron-accepting compound and (c) the reaction medium that determines the temperature at which the color-developing reaction of the both compounds takes place is enclosed in microcapsules;
the thermochromic pigment composition may be a thermochromic pigment composition having a microcapsular form of reversible thermochromic composition/wall film=7/1 to 1/1 (weight ratio);
the thermochromic pigment composition may have a non-round particle cross section; or
the thermochromic pigment composition may be a pigment composition having a hollow at some part of a particle outer surface; or
the thermochromic pigment composition may be a pigment composition selected from any one of a heat-color-extinguishing type capable of color-extinguishing upon heating from a color-developed state and developing a color upon cooling from a color-extinguished state, a color-memorizing type capable of memorizing a color-developed state and a color-extinguished state alternately in a specific temperature region, and a heat-color-developing type capable of developing a color upon heating from a color-extinguished state and restoring to the color-extinguished state upon temperature drop from a color-developed state.
The present invention also provides a fiber processed article comprising a plurality of filaments of long fibers or short fibers of the above thermochromic acrylic synthetic fiber, having a single-fiber external diameter of from 1 xcexcm to 100 xcexcm; the filaments being made into a bundled, close-contact or massed state.
The present invention still also provides a process for producing a thermochromic acrylic synthetic fiber, comprising the step of;
subjecting to wet spinning a spinning dope comprising a concentrated aqueous inorganic salt solution in which an acrylonitrile polymer has been dissolved and in which a thermochromic pigment composition with an average particle diameter of from 0.5 xcexcm to 30 xcexcm is dispersedly blended in an amount of from 0.5% by weight to 40% by weight based on the weight of the polymer; the pigment composition containing (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound and (c) an reaction medium that determines the temperature at which the color-developing reaction of the both compounds takes place.
In the above process, the concentrated aqueous inorganic salt solution may contain as a chief component a thiocyanate or zinc chloride.